Boundary Layer Profile
 

Hi,

I am analyzing the effect of a 2D roughness element in a Blasius boundary layer. So I insert the boundary layer as a profile at the inlet. Its thickness at this point is about 5mm. Now, the issue is at the very next node Fluent reduces the boundary layer thickness to about 0.5mm even though the geometry at this point is still a flat plate. I am wonder why this is the case. Theoretically, the boundary layer should grow as it progresses along the plate.

The major conditions are:
Inlet: Blasius profile
Wall: No-slip
The flow is laminar. No turbulence model.
Transient.

If someone could explain to me why this occurs it would be greatly appreciated.